hey..
i apologise for my spelling in advance...
i know this thread was from a long time ago, but thought i would reply incase any newbee's have a look.
im from cornwall, near falmouth, and a great little place to grab muscles and other shellfish is up by pendennis point, head to little pendennis castle, not pendennis castle, its a little point a minute away, with a car park and look out points from the war (about two minutes drive from gulienvase beach) not only is this a beautiful spot, but the rocks are easily accesible and there are tonns of muscles here, and the rockpools have shrimp (tide dependent).
another great place is in mylor, mylor bride i think (just ask for the port) here, every evening, a bunch of locals bring their fishing rods and catch macrel for their tea as the tides change, you are almost alway sgarenteed to catch something here (although havnt been for a few years as im a veggie now). not only this but pollock is a common catch too. be careful or the garr fish, these are common and too bony to eat, but they make great bate. not only this but big crabs cling to the harbor wall here, and a bit of string with bread on it is a definate fave, i've never cooked a crab from here, but we would catch them quite easily and throw them back in the water.
in the warmer months, blackberries boom in cornwall, remeber not to pick them from foot level cos dogs will have peed on them, and also avoid those from the roadside, if you ask any local, most will have a fave spot for picking.
if you check out the local book stores (theres a waterstones in truro) there are a wide selection of books about places to forrage in cornwall etc, so it might be worth checking out one of those to.
good luck